package lecture06.circle;

import java.util.Scanner;

class Circle {
    double radius;
    public double area() {
        return Math.PI * radius * radius;
    }
}




public class CircleInf {
    public static void main(String[] args) {
        Circle circle = new Circle();
        Scanner sc = new Scanner(System.in);
        circle.radius = sc.nextDouble();
        System.out.println("area:" + circle.area());

    }
}
